This invention relates to the cooling of electronic equipment enclosed within a security cabinet.
As a result of global deregulation of the telecommunications industry, telecommunication service providers are obliged to allow access to their competitors into their central offices. There is a growing practice to locate telecommunications equipment from competing vendors in a common office area and, in consequence, security of their equipment and integrity of their telecommunication services are of serious concern to service providers. It is possible that the integrity of unsecured equipment may be inadvertently disrupted by unauthorized craftsmen during the performance of their work function in a common office area. For this reason, security cabinets are now being used, on an increasingly widespread basis, to house telecommunication equipment, e.g. in central offices. There is a wide variety of telecommunications equipment that must be secured to ensure operational integrity. This includes central office equipment, switches, routers and mobile switching centers. In addition, it may be found prudent or necessary for various reasons to house electronic equipment, other than telecommunications equipment, within security cabinets. Such other electronic equipment may include electronic control or operating mechanisms as used in industry.
During use, electronic equipment is known to generate heat. Unfortunately, operational components, such as surface mount components, e.g. integrated circuit components, of electronic equipment, operate correctly only when their operational temperatures are maintained below certain limits. Above such temperatures, incorrect component operation is known to result, thereby causing either incorrect operation of the equipment or its complete breakdown or premature failure. Hence, it is essential to remove heat and heat removal includes passing cooling air through the equipment for heat extraction.
In published descriptions of electronic equipment housed within security cabinets, such as in published Patent Applications, for example WO 00/21372 and AU 9183401, cooling air passes along interconnected in-series pathways, i.e. from ambient atmosphere into a cabinet chamber, from the cabinet chamber through the equipment and then back into the cabinet chamber before being forced as heated air back outside the cabinet. A problem with this published type of cooling is that it is known that the presence of the cabinet deleteriously affects the efficiency of the cooling process. A reason for this is that the air temperature within the cabinet chamber is raised by the heated air issuing into it from the electronic equipment and also by heat radiation and heat conduction from the equipment into the chamber. Hence, while the chamber temperature ranges are lower than those within the equipment, the heated air within the chamber acts to heat insulate the equipment from the ambient atmosphere. Thus heat is not extracted from the electronic equipment at such an advantageous rate as would be the case without the use of a security cabinet.
Generally speaking, electronic equipment designed for central office telecommunications applications may operate correctly and efficiently within a normal temperature range e.g. of between 5 and 40 degrees centigrade. However, when housed within security cabinets, the operating temperature of any electronic equipment will increase, and there is a potential danger of sufficiently high temperatures developing to harm the equipment. Five or more years ago, a single unit of electronic equipment, such as telecommunications equipment, may have been operating at 500 watts of power. Cooling methods at that time adequately dealt with sufficient heat extraction to easily maintain operating temperatures within the required normal range. Even when multiple units of equipment were housed together, excessive power was not used, e.g. three units required only about 1.5 kW of power, and temperature control was again easily maintained. However, as further development has taken place, circuitry has become more complex and dense upon printed circuit boards and with the use of more closely packed and great numbers of circuitry components, a single unit of electronic equipment is now operating at 4 kW of power. This is well beyond that required for the three previous units referred to above. It is also now known to use two units together, each requiring 4 kW of power with a resultant 8 kW of power.
As may be seen therefore, over about the last five years it has become progressively more difficult to extract heat from electronic equipment at sufficiently high rates to maintain operating conditions within the desired operating range of temperatures. The use of security cabinets has increased this difficulty because of the heat insulating effect provided by them. For instance, with the recently designed high powered equipment, operating temperatures within a security cabinet chamber may be extremely high, e.g. 15 degrees centigrade or higher, compared to room temperature. This leads to extremely high operating temperatures within the equipment, e.g. 15 degrees centigrade higher than would be the case without the use of a security cabinet. With a required highest operational temperature being 40 degrees centigrade, for example, it may be seen that such a temperature may easily be exceeded when the more recently designed equipment is installed within security cabinets.
In efforts to overcome the above practical cooling problems, some vendors of electronic equipment and security cabinets have advocated placing heat exchangers or air conditioners inside cabinets. The addition of such further equipment requires significant infrastructure costs to the installer and high risks of costly damage to electronic equipment in the event of cooling equipment failure or of leakage of fluids used by heat exchangers and air conditioners. Understandably, telecommunications service providers are often unwilling to deal with the additional cost, risk, and complexity of adding this additional equipment to their installations. For these reasons also, telecommunications service users wish to avoid heat exchangers or air conditioners inside cabinets.
In addition, suggestions have been put forward to create specific pathways for cooling air through chambers of security cabinets on the cooling air inlet and output sides of electronic equipment. This is for the intended purpose of avoiding heat buildup in cabinet chambers. When put into practice, however, the structures have been ineffective in eliminating the heat extraction problem. In one of these structures, electronic equipment is housed within a cabinet having its chamber separated by partitions into an air intake side and an air outlet side. Cooling air received into the air intake side of the chamber is caused to flow through the equipment to be exhausted into the air outlet side of the chamber before dissipation into ambient atmosphere. However, apart from having no noticeable effect on the heating problem, the structure is of undue complexity and requires the installer to mount the partitions to extend from walls of the cabinet to the equipment while being sealed in position. This presents added assembly problems.
As may be seen therefore, the above-related problems, while extremely important to solve in the light of present and advancing technology, have up to this present time, not been successfully addressed.
The present invention seeks to provide a structure for cooling electronic equipment within a security cabinet and a method of cooling which eliminates or diminishes the above problems.
According to one aspect of the present invention, there is provided a combination of a security cabinet and electronic equipment housed within the security cabinet, a cooling air flow passage arrangement for the electronic equipment, and an inlet and an outlet for the cooling air flow passage arrangement, and in which the inlet opens directly to the exterior of the cabinet to pass cooling air directly from a first spacial region, exterior to the cabinet, into the air flow passage arrangement, while substantially bypassing a chamber between the cabinet and the electronic equipment, to be expelled from the outlet and outwardly of the cabinet to a second spacial region exterior to the cabinet.
In use, the air entering the cooling air flow passage arrangement (referred to hereinafter in the description as xe2x80x9ccooling passage arrangementxe2x80x9d) directly from the spacial region is substantially at ambient atmospheric temperature, i.e. that outside the confines of the cabinet. Hence, this air is substantially unaffected by higher air temperatures within the cabinet chamber. Because the air entering the cooling passage arrangement is at substantially ambient temperature, it removes heated air from within the electronic equipment more effectively than would be possible if cooling air entered that arrangement entirely from the cabinet chamber, as this latter air is at a higher temperature than the ambient temperature.
In a preferred structure, all of the cooling air is drawn from the ambient atmosphere, i.e. while completely preventing any cooling air from entering the electronic equipment from the cabinet chamber. Hence, most effective cooling will occur with this preferred structure. In other structures consistent with maintaining operating temperatures within the electronic equipment within required limits, the inlet is provided to deliver a certain percentage of the cooling air to the cooling passage arrangement directly from the first spacial region, while other cooling air, which is warmer than that from the first spacial region, is introduced from the cabinet chamber. The resultant mixture of cooling air from both of these sources has a temperature lower than that of the air in the cabinet chamber alone. It follows that the resultant mixture will be more efficient in removing heat from the electronic equipment than cooling air entering from the cabinet chamber only. Therefore, while the preferred structure referred to above provides an optimal heat removal rate from the equipment, it is to be understood that the invention includes structures in which a certain percentage of cooling air is drawn also from the cabinet chamber with the proviso that the temperatures within the equipment are maintained below their desired upper operational limits.
In addition, equipment, in combinations according to the invention, conveys less heat from its walls into the air of the chambers of security cabinets, than is possible with prior constructions using security cabinets. Hence, temperatures within the whole of a cabinet and electronic equipment combination are maintained lower than has previously been possible.
Different practical structures are possible within the scope of the invention. In some practical structures, the inlet to the cooling passage arrangement is provided in a wall of the cabinet and a cooling air conduit extends from the inlet, across part of the chamber of the cabinet, to the electronic equipment. This conduit defines a first part of the cooling passage arrangement which is interconnected to a second part of the arrangement defined with the electronic equipment itself. Preferably, this conduit is substantially sealed so as to seal the air of the first part of the cooling passage arrangement from the chamber of the cabinet.
In a preferred construction using a conduit, the inlet is provided in a door arrangement of the cabinet. In practice, it may be convenient to provide the door arrangement in the form of two doors which are hinged at remote edges of the door arrangement with free edges of the doors being close together to form the wall when in closed positions. This results in the cooling air conduit being provided in two portions. The two portions are mounted one to each door to define part of the inlet in each door, and with the two portions having surfaces which, with the doors closed, oppose each other to form the conduit.
In another preferred structure, the cooling passage arrangement has a first portion extending beneath the equipment and a second portion within the electronic equipment and opening on to the first portion at an underside of the equipment. The inlet is provided in a lower portion of a wall of the cabinet to direct cooling air beneath the underside of the electronic equipment and through the passage arrangement.
The invention also includes a method of cooling electronic equipment housed within a security cabinet comprising moving a stream of cooling air directly from a first spacial region exterior to the cabinet into and through a cooling passage arrangement of the electronic equipment, while substantially bypassing a chamber defined between the cabinet and the electronic equipment, and then passing the stream of cooling air into a second spacial region exterior to the cabinet.